The layout of the universal QWERTY keyboard is familiar to all typists and computer users. In this configuration, each alphanumeric symbol is assigned a unique key. This configuration has dominated text input systems (including typewriters and computers) for over a century. In recent years, however, the development of new technologies like mobile telephones, personal digital assistants (PDAs), and wireless two-way messaging devices has lead to a reconsideration of the configuration of keypads or keyboards. For example, in the case of mobile telephones, three or more letters have been assigned or associated with each numeric key. In the case of some two-way wireless messaging devices, to conserve space the devices have been designed with a two-symbol-per-key keyboard. For example, such a device may feature a reduced-key QWERTY keyboard, wherein the conventional QWERTY layout is maintained, but two adjacent letters are associated with each key, e.g. one key is used for entering both the letters “E” and “R”.
In a reduced-key input device, the keys have an associated sequence of alphanumeric symbols or characters. For example, a key may be associated with the letters JKL, as is the case with the “5” key on a telephone keypad. Devices that use a reduced-key input interface for receiving text input typically operate in one of two modes. The first mode is a “multi-tap” mode. In multi-tap mode, the user selects one of the alphanumeric symbols or characters associated with a key by hitting the key a number of times in succession corresponding to the position of the symbol in the sequence. For example, to enter the letter “J”, the user hits the “5” key once. To enter the letter “L”, the user hits the “5” key three times.
Another mode of operation is a predictive mode in which the user only hits the key associated with the desired symbol once, without specifying which of two or more symbols the user actually wants. Once the user has pressed a number of keys, the device uses predictive algorithms to attempt to guess which of various possible combinations of symbols the user was most likely attempting to define. The user may be provided with a pick-list of candidates for selection. In this mode, the user only enters one keystroke for each desired symbol or character.
When operating in the multi-tap mode, a difficulty arises in entering two successive symbols when those two symbols are associated with the same key. For example, in a two-symbol-per-key context a key may be associated with the letters ER. When a user strikes this key three times in succession it creates an ambiguity in determining the desired input. Three keystrokes may mean the user wants to enter RE, or ER, or EEE.
To resolve this ambiguity, devices operating in multi-tap mode typically employ a default rule, whereby the first two keystrokes will be interpreted as a multi-tap selection of the letter R. Because the user has reached the end of the sequence associated with the key, the next keystroke is interpreted as being associated with the input of a new character, i.e. the letter E. Accordingly, the default understanding of three keystrokes is an output of RE.
To overcome this default rule and obtain an alternative output, like ER or EEE, the device may provide the user with a “next” key to indicate that the user is done selecting a character and that the cursor should be advanced to the next location. Subsequent keystrokes will be interpreted as the input of a new character. Accordingly, to input ER, the user would strike the “ER” key once, hit the “next” key, and then strike the “ER” key twice.
Another method of overriding the default rule is to wait for a timeout to occur. Typically, multi-tap input devices will provide a “timeout” feature, wherein the device presumes that a user is finished inputting a character if a sufficiently long period of time elapses following a keystroke. If a timeout occurs, then the device may advance the cursor to the next location in a text field on the presumption that any subsequent keystrokes will relate to a new character. Accordingly, to input ER, the user would strike the “ER” key once, wait until the cursor advances, and then strike the “ER” key twice.
It will be appreciated that using the “next” key to manually advance the cursor to the next location, or waiting for a timeout to automatically advance the cursor, results in a text input system that interferes with a user's keystroke cadence or rhythm. Accordingly, a need exists for another method of resolving multi-tap text input ambiguities.